Studies on the sediments of Vembanad Lake, Kerala state Part III Distribution and interpretation of bottom sediments

Abstract

Distribution patterns of FE, Mn, Ti, Ni, Co and Cu in sediments of Vembanad Lake and adjoining river systems have revealed that (1) elemental concentrations follow closely the texture of the sediments, (2) river sands contain very low concentrations of all elements, (3) in the lake sediments the elemental concentrations increase with decrease in grain size, (4) even among the fine-grained sediments, the sediments in the estuarine region are impoverished in their Mn and Co contents and enriched in their Ni and Cu contents as compared to fine-grained sediments in other parts of the lake and (5) Fe, Mn, Ni, Cu and Co bear significant relationship with organic matter of the sediments Distribution patterns of elements in the non-estuarine region of the lake (between Arakutti and Alleppey) where sediments are mostly deposited in a fresh water environment are controlled largely by grain size, textural characteristics and mineralogy of sediments On the other hand, differential behaviour of elements in the estuarine region has been attributed to several factors The impoverishment of Mn and Co can be due to (i) desorption of these elements from the river borne detritus on coming into contact with saline waters, (ii) dredging operations which may lead to the release of these elements into the waters and (iii) mixing with marine sediments containing low concentrations of Mn and Co The enrichment of Ni and Cu can be due to their association with (i) organic matter of the sediments, (ii) ferric and manganese hydroxides through adsorption and (iii) mixing with marine sediments which contain relatively higher concentrations of these elements